Radio telephone system



Dec. 2, 19M. A. F. BOWERS RADIO TELEPHONE SYSTEM Filed sept. 27, '1940INVENTOR BYQZOarel/S ATTO of the radio receiver and thereby disables it,while at the same time the lower front contact of the relay SR closesthe circuit of the radio transmitter BT. Likewise the middle frontcontact of the relay SR closes the circuit of the oscillator O so thatthe carrier current is now supplied to the radio transmitter. By merelymanipulating the key K the talker can disable the radio receiver andrender the radio transmitter operative while he talks, and uponreleasing the key the condition is reversed so that the radiotransmitter is disabled and the receiver is placed in operativecondition to receive talk coming from the shore station.

As will appear later, this switching operation, with its consequentcontrol of the carrier, is used at the shore station to alternatelypermit transmission to and from the radio transmitter and radio receiverrespectively. This control is effected in such a way that the radioreceiver I,

ashore is normally conditioned to receive and the path to thetransmitter is disabled. When no carrier is being sent out by the shipstation the operator ashore may, by plugging in, condition thetransmitter so that the ship may be signaled. If the land station is notcalling, however, the receiver ashore will receive the carrier sent outfrom the ship when its operator actuates the key K to call. After thecall has been answered by the shore operator and the carrier sent outfrom the ship ceases, the normal condition is reversed and the radiotransmitter ashore is put in operative condition and the receiverdisabled. Thus it is evident that the switching operation between radiotransmitter and radio receiver, both aboard ship and on shore, is underthe direct control of the key K on shipboard.

The radio transmitting and receiving apparatus ashore is indicatedschematically at C. The system illustrated by way of example is atelephone system adapted for communication with ships operating within alimited area such as a harbor, and includes a single radio transmitterST, which may be of any known type and is illustrated as a simple box. Avoice frequency amplifier AT is associated with the radio transmitterST. This equipment is connected by means of a wire line TL to switching,signaling and controlling apparatus at the marine operators position Aand the technical operators position B. Although the ship moves about sothat it is in different positions both as to direction and distance withrespect to the radio transmitter ashore, it has been found that a singletransmitter, located at a xed position, is sufficient for transmissionfrom the shore to a ship at any reasonable location.

Since it is not always possible to use a high power transmitter on boardship, it is desirable to have several receiving stations located atdifferent convenient points along the shore, so that in transmittingfrom ship to shore the nearest convenient shore receiving station can beused. Consequently at C two radio receivers, SR1 and SR2, areschematically shown. These receivers are of a known type and aretherefore illustrated by block diagrams. It will be understood, ofcourse, that more than two radio receivers may be provided if desired.These receivers SR1 and SR2 are connected by means of lines RL1 and RLz,respectively, with the apparatus at the technical operators position.

Each radio receiver ashore is provided with a codan (shown schematicallyat COD1 and COD2). The codan is of a known type and is therefore shownas a simple block. It receives its name from the fact that it is acarrier operated device which is as unresponsive as possible to noise,the name codan being formed from the initial letters of the phrasecarrier operated device antinoise. The normal function of the codan isto insert a high loss in the output of the radio receiver with which itis associated when no carrier signal is being received. As this is afunction with which the present invention 1s not concerned, suchcontrolling apparatus, which is well known in the art, is notillustrated.

Each codan is provided with a so-called codan relay illustrated at CR1in the case of receiver SR1, and at CRz in the case of receiver SR2. Thecodan relay may have two windings, one of these windings beingresponsive to a rectied current resulting from the selected carrier, andthe other being responsive to a rectiied current resulting from noise.The circuit of the codan which controls the carrier responsive windingmay be made sharply selective to the carrier while circuit controllingthe noise responsive v winding is made receptive to all frequencieswithin the side-band range except in the immediate vicinity of thecarrier. The result is that the codan relay has its armature thrown inone direction by means of the rectified noise currents when no carrieris being received. When, however, the carrier current comes in and isrectified, the rectified current in the carrier responsive winding ofthe codan relay causes the latter winding to predominate in its eectover the other winding and swing the armature of the relay to theopposite position. As shown, when the codan relay pulls up in responseto the reception of carrier, its armature connects ground to a simplexcircuit extending over the line RL1 or RLz as the case may be,connecting the radio receiver to the technical operators position.

The current thus transmitted over the simplex circuit is used at thetechnical operators position to perform various functions, including theactuation of a signal at the technical operators position. Also it hasbeen the practice, prior to the present invention, to use this currentto actuate the signal lamp at the marine operators position A. Inaccordance with the present invention, however, a relay ISi is includedin the simplex circuit operated by the codan relay which establishes anauxiliary circuit (X1 in the case of radio receiver SR1) leading tc thetechnic-al operators position, where the circuit may be used to effectthe setting of a switch under the control of the dial aboard ship, aswill be described later.

An example of apparatus for switching, signaling and otherwisecontrolling the transmission circuits is located at A and B-principallyat the latter position. A common transmission path or line L may beprovided and this may be switched to a transmitting line TL leading tothe radio transmitter ST orto a receiving path RL'leading to a receivingamplifier RA, the input of which accanto is branched to each of .severallines Ria, Bln', etc., leading :to individual radio receivers such asSR1 and SR2. The line L may be optionally switched tothe transmissionpath or the receiving path RL .under the control of a polar relay. SW,which is under the control .of the push `button K at the ship station D.The transmitting path 'TL may also include a .so-called vogad dor.automatically adjusting the gain of the transmission path ina mannerwell known in the art, its name being derived 'by using the initials Aofthe expression voice .operated .gain adjusting device. 'This device Iiswell known and, as it is not concerned with the present invention, isillustrated by 1a conventional box .or rectangle.

As already stated, the .input of the receiving amplified 'RA in thereceiving path 'RL may be branched to several transmission paths leadingto individual radio receivers. Each of these paths may include anequalizer and pad network of well known type, illustrated at RE1 and'REa The present invention Ais not concerned with Athe details of thesepieces :of equipment and, as they are well known, they are merelyrep-resented symbolically.

A polar relay C1 is associated with the path RL1 anda similar relay C2is associated with the path R112. Each of these relays has a lower.biasing winding. 'The upper winding in each case is connected to thesimplex circuit previously described as controlled by the codan relays1CR1 and CB2. The middle winding 'is .connected to another simplexcircuit with which we are not here concerned, Aso that it has `not beenillustrated. For purposes of the present invention it is sufficient toknow that when the codan relay CB1, for example, connects ground to thesirnplex circuit Yassociated with the upper winding of the polar relayC1, the armature of said relay will be shifted from .its back contact toits front con tact to produce certain .effects `which lwill be .desribed`in more detail later.

Dnc of these eiects is to cause xthe .operationof the technical.operators lamp TOL when 'the carrier (or interference) causes theoperation of the codan relay. In systems of the vprior art the actuation.of the relay C1 also energized the signal lamp at vthe marine operatorsyposition to apprise .the :operator that an incoming call was being madefrom the ship at D. Since, however, the .codan sometimes operated inresponse to interference, false signals would -.be received by themarine .operator and to .avoid this the marine operators .call MOL1 andM0112 are actuated by a dial-controlled switching arrange ment about tobe described. Whether the lamp M0111 or the lamp MOLZ vis to be useddepends upon which .one of the receivers lSR1-or SR2 lis close r.enoughto the ship at D to receive its signal.

While .any .suitable dia'lFcontrolled switch may be utilized, the switchherein illustrated -is of the upaand-.arouhd type frequently used instep-bystep automatic .switching systems. vThe switches which controlthe vlamps MOL1 and MOLe, `respectively, .are separately controlledythrough the radio receivers SR1 and SR2. As they are identical,however, .only one need be described. The Vswitch Vwhich is controlledfrom the receiving radio receiver SR1, for example, comprises a wiper W1shown at position B, 'fwhich, under the control of a vertical steppingmagnet "V1, may be stepped vertically to the level `oi any one .of tenbanks of contacts, .each having ten contacts in .each bank. 'This actionis taken by the switchin response to the *first digit sent by the dialSD at the ship station D.. In response to the' second digit dialed, thewiper W1 will be rotated stepby-step by the 4'rotary magnet R1 to aparticular contact inthe vertical row or level to which the wiper hasbeen previously elevated.

As shown, .if the number 5,0 is dialed, the flrst five impulses willelevate the wiper W1 to the fth row of contacls, and the succeeding ten:impulses 'will rotate the wiper to the ytenth contact in that row tocomplete the circuit .of the marine operators lamp MOL1, therebyindicating that .a call has come in. When the train of carrier wavessent out from 4the ship `'cornes to an end the release :magnet Y1restores the switch to normal in aweii-kno-wn manner. The stepping cithe .switch is `controlled by relay IT1, connected to an auxiliarycircuit Xi leading to the distant radio receiver .SR1 and operated bythe relay 151 under the .control of the codan relay CR1. A similar relayIIa, controlling the .switch associated with the path Le, is operatedover an auxiliary cir.- cuit Xe lfrom the radio receiver SR2.

The marine .operator is provided with jacks J1 and J2 :for completingthe connection in the case of a call signal received from .either of theradio receivers illustrated, it being understood that any desired numberof radio receivers may be employed, :in which case there will be anadditional jack :or each additional receiver. If the dial .signai1received 'by the radio receiver SR1 so that the marine operators lampMOL1 is actuated, the marine operator will plug in to the jack J1. 1f.,on'the other hand, the signal is received from the radio receiver the.operator will gc in on the jack J2.

.es soon as the operator plugs in, the sleeve relay .Si is loperated tovdisable the signal lamp. The relay S1 may also provided with an extraContact `to open the circuit by which relay IT1, operates relay LR1,thus` preventing operation of the switch during conversation. Relay S1also actuates a secondary relay S2. The latter in conjunction with thepolar relay C1 .controls certain switching operations which will be morefully described later. By one of these switching operations 'the Acommonreceiving vcircuit RL is extended to the receiving branch path circuitleading to the radio receiver which is receiving the :signal from theship. Another of these switching operations, which is ultimately con.-tro'lled vhy the push `button K at the ship station, is the switching ofthe common path L between the transmitting path TL and the receivingpath xThe relay 'REC1 completes the .connection from `the .commonreceiving path RL to the indivdual receiving path `RL1, and thecorresponding relay associated with the receiving path R112 will .(in.case .the signal is 'being -received from the 4radio receiver SR2).connect the common receiving path RL to the individual receiving pathR112.

Further .details of .the system 'will be better apprehended from adescription of the operation, which is as follows:

Let us suppose that the ship at D is located nearer to the radioreceiver SR1 than to the radio receiver SR2. In the normal condition ofthe circuit the polar relay SW is actuated only by its upper orbalancing winding and holds its arma-ture in .such .a position as toclose the connection from the common path L to the common receivingvpath RL, .the :transmitting path being disconnected from .the :commonpath 1L. At the ship station, in .the normal condition of;

the circuit, the push'button K is not actuated and consequently therelay SR is deenergized, so that the radio receiver BR is in receivingcondition. When this condition obtains, the' radio transmitter BT isdisabled. l

If, now, some one aboard ship desires to telephone, he presses the pushbutton K and operates the dial SD to dial the combination which willoperate the marine operators line lamp. In the instance illustrated,this will be accomplished by dialing 50. As soon as the push button isoperated the relay SR is energized to open the circuit of the radioreceiver BR and close the circuit of the radio transmitter BT.. At thesame time it also closes the circuit of the oscillator O to supply thecarrier to the radio transmitter. The carrier, upon being transmitted,will be received by the radio receiver SR1 and will operate the codanrelay CR1, which in turn completes a circuit through the relay IS1 overthe lower side of the path RL1 to the upper winding of the polar relayC1. This causes the polar` relay C1 to shift its armature to its lowercontact. This completes a circuit for the relay FL from battery throughsaid relay over the lower back contact of the relay REC1, front contactof polar relay C1, upper back contact of relay REC1, and back contact ofrelay SCO to ground. Relay FL opens the circuit of normally energizedslow release relay T, which completes a circuit through the upperwinding of the relay INC. Relay INC completes the circuit for the lampTOL at the technical operators position.

In circuitsY employed prior to the presentinvention the connection abovedescribed was extended also to the marine operator's lamp MOL1. With thecircuit wired in accordance with the present invention, any conditionthat operates the codan relay CR1 will operate the lamp TOL at thetechnical operators position, whether it be the ship calling or aninterfering condition, but the marine operators lamp MOL1 will not beoperated.

In accordance with the present invention, it is necessary for the callerat D to do something more than merely press the key K in order to callthe marine operator at A. After depressing the key K the caller mustnext operate the dial SD to interrupt the carrier in accordance with acode. In the present instance it will be assumed that the code dialed is50. This will first interrupt the carrier ve times. The fifthinterruption is followed by a spurt of carrier, and then the carrier isinterrupted ten times in succession. It will be noted that when thecarrier is sent out by depressing the key K, the codan relay CE1operates the relay IS1. This in turn completes a circuit from groundover the front contact of said relay and over the conductor X1 (whichmay be a simplex circuit derived from a spare pair), and through thewinding of the relay IT1 to battery. Relay IT1 completes a circuit f'orthe pulsing relay LR1, which at its front contact completes a circuitfor the slow release relay D1, which will be held up duringinterruptions of the carrier due to dialing. A circuit is prepared forthe vertical magnet V1 over the front contact of the slow release relayD1, but this circuit is not completed so long as the carrier remainsuninterrupted.

When the dial SD is operated, the first interruption of the carriercauses a momentary release of the relay IS1 at C, with the consequentrelease of the relay I'Ii at B. The armature of the pulsing relay LR1falls oi and completes a circuitover` its back contact from ground,overthe front contact of slow release relay D1, over the normalleft-hand contact of the off-normal switch ON, through slow releaserelay D1 and through the vertical relay V1 to battery. The pulsevthrough the vertical magnet V1 lifts the wiperl W1 one step, bringingit on a level with the rstrow of contacts. At the end of the impulse thearmature of the pulsing relay LR1 is again drawn up and is followed bythe second interruption of the carrier, which again causes the armatureof relay LR1 to fall back and complete a circuit from ground over theback contact of said relay, over the front contact of the relay D1 andover the left-hand alternate contact of the oli-normal switch (ON), andthence over the front contact of slow release relay D1', through thewinding of relay D1 and through the vertical magnet V1 to battery. Thissecond pulse through the vertical relay elevates the wiper W1 anotherstep. It will be noted that the pulsing circuit for the vertical magnetV1 is now completed over the front contact of the slow release relayD1', which remains energized during pulsing interruptions of thecarrier. Successive interruptions of the carrier in dialing the digit 5send additional pulses over the back contact of the pulsing relay LR1and through the vertical magnet V1, over the circuit just described,thus stepping the wiper W1 to the fifth row of contacts of the switch.

At the end of the iifth interruption the carrier is transmitted for alonger time than during the periods between dialing impulses and thispermits the slow release relay D1 to fall oi so that its armature is onits back contact. When the caller at station D dials the firstinterruption of the ten impulses representing zero, the firstinterruption causes the pulsing relay LR1 to fall oi as before. Thistime it completes a circuit from ground, over the front contact of theslow release relay D1, over the left hand alternate contact of theolf-normal switch ON, over the back contact of the slow release relayD1', through the slow release relay D1 and through the rotary magnet R1to battery. The slow release relay D1 opens the circuit from battery tothe wiper W1 during the rotary stepping operation and holds it openuntil the end of the series of interruptions due to dialing. This irstimpulse through the rotary magnet R1 steps the wiper W1 horizontal tothe first contact in the fth row, and successive interruptions of thecarrier, due to dialing, successively advance this wiper horizontallyuntil it rests upon the last contact of the fifth row.

At the end of the dialing operation the slow release relay D1 falls olfand a circuit is completed from battery over the back contact of saidrelay, over the wiper W1 and the tenth contact in the fth row, and overthe back contact of the relay S1 to the lamp MOL1, causing the lamp toglow to apprise the marine operator that a call has come in. If desiredanother lamp, located at the technical operators position, may be usedin parallel with the lamp MOL1 beyond armature of relay S1, so that thetechnical operators position will be signalled also by this dialingoperation. It will be noted that the slowy release relay D1 ismaintained energized from the time the carrier is applied at station Dthrough all of the momentary interruptions due to dialing, until suchtime as the carrier is interrupted by releasing the key K.

As soon as the marine operator notes that the lamp MOL1 is glowing, sheknows that a call has come in through the radio receiver SR1. Of course,had the call come in through the radio receiver station SR2, the dialingoperation would have actuated the wiper W2 associated with the circuitL2 and would have caused the lamp MOLz to glow, which would haveindicated a call from the radio receiver SR2. The operator now plugsinto the jack J1, thus operating the relay S1 over the sleeve circuit.At its left-hand armature the relay S1 opens the circuit of the signallamp MOL1 and at its right-hand front contact it completes a circuitthrough the relay S2.

Relay Se at its upper front contact completes a circuit from groundthrough the winding of relay REC1 which at its upper contact extends thecircuit RL to the branch circuit RL1 leading to the output of radioreceiver SR1. At its middle contact relay REC1 shifts the groundconnection for the armature of the polar relay C1 from the back contactof the relay SCO to the front contact of the middle armature of relayREC1. `At its lower front contactrelay REC1 opens the circuit of relayFL which, acting through relays T and INC, opens the circuit of the lampTOL at the technical operators position. The lower armature of the relayREC1 at its front contact completes the circuit from ground over itsmiddle front contact, over the front contact of the polar relay C1(carrier now being received so that this relay is actuated), over thelower front contact of relay REC`1, and through the winding of relaySCO, which latter relay is operated.

This condition obtains so long as the push butvton K is actuated by thecaller at station D. Consequently, from the time the operator answersthe call at jack J1 until the push button is released the relay REC1maintains a connection from the common receiving circuit RL, over' theupper front contact of the relay REC1, to the receiving circuit RL1connected to the radio receiver SR1 at station C. The relaycorresponding to REC1, associated with the receivingy circuit RLz is notactuated, and consequently the latter circuit is not connected to thecommon receiving circuit RL. It will also be noted that the circuitthrough the lower winding of the polar relay SW is held open by thepolar relay C1 because its armature is on its front contact so long asthe carrier persists. Consequently, the radio receiver SR1 is duringthis period connected over the receiving circuit RL1 through theequalizer pad RE1 over the upper front contact of the relay REC1,through the receiving amplifier RA, over the common receiving circuitRL, and over the lower or front contact of the polar relay SW, andthence over the common circuit L to the branch L1 o'i said circuitleading to the jack J1. The operator is now able to hear anything saidby the caller at station D.

In order that the caller at station D mayv know that the operator' isasking him for information as to the connection desired, he mu'st, as'soon as he has dialed the operator, release the push button K, thusdisabling his transmitter BT and putting his radio receiver BR inoperatingv position. This is done throughl the release of the relay SR.The consequent interruption of the carrier at the radio transmitter BTcauses the codan relay CR1 to fall off and release the relay S1V at Cand open the circuit through the upper winding of the polar relay' Cr atB1 Polar relay C1 now shifts its armaturev to its upper back contact andthereby completes a circuit from ground over the middle front contact ofrelay REC1, over the upper contact of the polar relay' C1, over thelower contact of relay S2, and through the lower winding of the polarrelay SW to battery. This shifts the armature of the polar relay fromits lower contact to its upper contact, thereby opening the receiverconnection through RL and completing the connection from the jack J1,over the circuit L1, common circuit L, and over the transmitting circuitTL to the radio transmitter ST. The operator is now able to talk. to thecaller at D from the radio transmitter ST through the radio receiver BR.

The release ci the relay IS1, just referred to, and which resulted fromthe release of the key K at D, disconnects ground from the circuit X1and thereby causes the release of the relay IT1. This in turn releasesthe pulsing relay LR1, whose armature is restored to its back Contact,and as rsoon as the slow release relay D1 releases, a circuit iscompleted from ground over the back contact of the pulsing relay LR1,over the back contact of the relay D1, over the right-hand contact ofthe oli-normal switch ON, through the release magnet Y1 to battery. Therelease magnet now restores the switch wiper W1 to normal so thatswitching apparatus is now ready to respond to a new rdialing operation.

The caller at D, having heard the operator challenge his call, nowpushes the button K, with the result that the relay SR disables hisradio receiver BR and applies carrier to his radio transmitter. Thisoperates the codan relay CR1, and again completes the circuit fromground through the relay IS1 and over the simplex circuit of the pairRL1, through the upper winding of the polar Yrelay C1. Polar relay C1now shifts its armature to its lower or front position and this opensthe circuit of the lower winding of the polar relay SW. The relay SWaccordingly shifts its armature to its lower contact and the 'circuitfrom the jack J1 isnow shifted from the transmitting line TL tothereceiving line RL1 and the caller is able to talk to the operator.

After the operator has completed the connection the caller may talk tothe party with whom he is connected by operating the key K to transmitthe carrier and releasing the key whenever he wishes to hear theresponse of the called party.

The relay REC1 of course remains operated so long as the connection isestablished at the jack J1. When the called party hangs up his receiver,the operator may receive'a disconnect signal and withdraw the plug fromthe jack J1; This releases the relay S1, which in turn releases therelay S2. Relay S2, upon being restored to normal, opens the circuit ofthe relay REC1, which releases and opens the circuit of relay SCO sothat the apparatus is restored to normal.

It will, or course, be evident that when no call isbeing sent out fromthe ship station at D and with the apparatus at stations A and B innormal condition, the circuit L will be conditioned to receive, as thelower winding of the polar relay SW will'be open-circuited at thecontacts of the relay S2 and corresponding relays. The biasing windingof said relay SW will therefore pull the armature to its lower contact,completing the circuit from the path L to the path RL. Under theseconditions the marine operator at A may at any time signal thev ship byplugging into the jack J1, thus energizing relays S1 and Sa insuccession, so that a circuity is completed from ground over the backcontact of relay SCO, over the middle back contact of the polar relayC1, the upper or back contact of the polar relay C1, and over the lowerfront contact of relay S2 through the lower winding of the polar relaySW. The current through the lower Winding of the polar relay SW willshift its armature so that the path L will be connected to thetransmitting path TL. The operator may now signal over the path TL bysignaling equipment (not shown) and can, of course, talk over said pathand through the radio transmitter ST at station C and radio station BRat station D in an obvious manner.

The dial equipment at ship station D and the step-by-step switchingequipment at station B may be utilized for other purposes than thosealready described. For example, with the circuit as shown, the shipoperator can send a signal to indicate dangers to navigation by dialing80. This will cause the wiper W1 (or W2 as the case may be) to beelevated to the eighth row of contacts and stepped around to the tenthcontact in that row, thus completing a circuit for the lamp DNL at thetechnical operators position, and, if desired, other lamps may beconnected to the same circuit located at other positions where it isdesired that this signal shall appear. An urgent call may be indicatedby dialing 07, which requires ten interruptions and will step the switchwiper W1 to the tenth row, and the seven impulses following will step itaround to the seventh contact in that row, completing the circuit in theurgent call lamp UCL. This lamp, and other lamps on the same circuit maybe wired to appear at any desired point. A distress call may be made bydialing 03, in which case the wiper W1 will be stepped up in the tenthrow and the third contact in that row, completing the circuit of thedistress call lamp DCL, which likewise may be wired to appear at anydesired point. If it is desired to dial the technical operator directlywithout calling the marine operator a lamp TOL' may be actuated bydialing the code 70, for example.

Instead of lamps it will be understood that audible signals such asgongs may be used, or if preferred, both gongs and lamps may beemployed.

What is claimed is:

1. In a ship shore radio telephone system, a land radio station havingpaths from a common terminal to a normally disabled radio transmitterand to a radio receiver normally conditioned for operation, meansoperable at will to extend said common terminal to a land circuit, aship station having a normally disabled radio transmitter and a radioreceiver normally conditioned for operation, means at said ship stationto disable the radio receiver thereat and to condition said radiotransmitter at the ship station to send out a carrier wave, means atsaid land station conditioned by the extension of a connection from thecommon terminal of said land radio station to a land circuit to maintainthe radio transmitter at the land station in disabled condition onlywhen. the carrier frequency is being received from the ship station, andoperable only when so conditioned to disable the radio receiver at theland station and to condition the radio transmitter thereat foroperation when no carrier is transmitted from the ship station, asupervisory signal device at the common terminai of said land station,and means to interrupt the carrier from the ship station in accordancewith a code, said supervisory signal device at said common terminalbeing actuated only in response to said code.

2. In a ship shore radio telephone system, a land radio station havingpaths from a common terminal to a normally disabled radio transmitterand to a radio receiver normally conditioned for operation, meansoperable at will to extend said common terminal to a land circuit, aship station having a normally disabled radio transmitter and a radioreceiver normally conditioned for operation, means at said ship stationto disable the radio receiver thereat and to condition said radiotransmitter at the ship station to send out a carrier wave, means atsaid land station conditioned by the extension of a connection from thecommon terminal of said land radio station to a land circuit to maintainthe radio transmitter at the land station in disabled condition onlywhen the carrier frequency is being received from the ship station, andoperable only when so conditioned to disable the radio receiver at theland station to condition the radio transmitter thereat for operationwhen no carrier is transmitted from the ship station, a signal means atthe land station responsive to a current of carrier frequency from theship station or from an interfering station to produce a signal at theland station, a supervisory signal device at the common terminal of saidland station, means to interrupt the carrier from the ship station inaccordance with a code, and means at the land station responsive to thecode but unresponsive to interference to actuate said supervisory signaldevice at said common terminal.

3. In a ship shore radio telephone system, a land radio station havingpaths from a common terminal to a normally disabled radio transmitterand to a radio receiver normally conditioned for operation, meansoperable at will to extend said common terminal to a land circuit, aship station having a normally disabled radio transmitter and a radioreceiver normally conditioned for operation, means at said ship stationto disable the radio receiver thereat and to condition said radiotransmitter at the ship station to send out a carrier wave, means atsaid land station conditioned by the extension of a connection from thecommon terminal of said land station to a land circuit to maintain theradio transmitter at the land station in disabled condition only whenthe carrier frequency is being received from the ship station, andoperable when so conditioned to disable the radio receiver at the landstation and to condition the radio transmitter thereat for operationwhen no carrier is transmitted from the ship station, a signal means atthe land station responsive to a current of carrier frequency from theship station or from an interfering station to produce a signal at theland station, a supervisory signal device at the common terminal of saidland station, means at the ship station to interrupt the carrier sentout from the ship station in accordance with a code, a selectivearrangement at the land station arranged to actuate said supervisorysignal in response to the carrier frequency from the ship wheninterrupted in accordance with a particular code, but not actuating saidsignal in response to steady carrier, or carrier interrupted by adifferent code, or in response to interference.

4. -In a ship shore radio telephone system, a land radio station havingAa normally disabled radio transmitter and a plurality of radio re.-ceivers each normally conditioned for operation, a short controlling andswitching point at which connections may be completed from a landcircuit to said transmitter and from any of said receivers to said landcircuit, a ship station having a normally disabled radiotransmitter Yanda radio receiver normally conditioned for operation, means at said shipstation to disable the radio receiver thereat and to condition saidradio transmitter at the ship station to send out a carrier wave, meansconditioned by the extension of a connection to a land circuit throughsaid controlling and switching point to maintain the radio transmitterat the land station in disabled condition only when the carrierfrequency is being received by one of said radio receivers at the landstation, and operable only when so conditioned to disable all of saidradio receivers at the land station and condition the radio transmitterthereat for operation when no carrier is transmitted from the shipstation, a supervisory signal device at said switchingpoint, and meansto interrupt the carrier from the ship station in accordance with a codeto actuate said supervisory signal device at said switching point.

5. In a ship shore radio telephone system, a land radio station having anormally disabled radio transmitter .and a plurality of radio receiverseach normally conditioned for operation, a shore controlling andswitching point at which connections may be completed from a landcircuit to said transmitter and from any of said receivers to a landcircuit, a ship station having a normally disabled radio transmitter anda radio receiver normally conditioned for operation, means at said shipstation to disable the radio receiver thereat and to condition saidradio transmitter at the ship station to send out a carrier wave, meansconditioned by the extension of a connection to a land circuit throughsaid controlling and switching point to maintain the radio transmitterat the land station in disabled condition only when the carrierfrequency is being received by one of said radio receivers at the landstation, and operable only when so conditioned to disable all of saidradio receivers at the land station and condition the radio transmitterthereat for operation when no carrier is transmitted from the shipstation, a signal means at the land station responsive to a current ofcarrier frequency from the ship station or from an interfering stationto produce a signal at the land station, a supervisory signal device atsaid switching point, means to interrupt the carrier from the shipstation in accordance with a code, and means at the land stationresponsive to the code but unresponsive to interference to actuate saidsupervisory signal device at said switching point.

6. In a ship shore radio telephone system, a land radio station having anormally disabled radio transmitter and a plurality of radio receiverseach normally conditioned for operation, a shore controlling andswitching point at which connections may be completed from a landcircuit t/o said transmitter and from any of said receivers to said landcircuit, a ship station having a normally disabled radio transmitter anda radio receiver normally conditioned for operation, means at said shipstation to disable the radio receiver thereat and to condition saidradio transmitter at the ship station to send out a carrier wave, meansconditioned by the extension of a landward connection to a land circuitthrough said controlling and switching point to--maintain the radiotransmitter at the land station in disabled condition only when the.carrier frequency is being received by one of said radio receivers .atthe land station, and operable only when so conditioned to disable theradio receivers at the land station and .condition the radio transmitterthereat for operation when no carrier is transmitted from the shipstation,a signal lmeans at the land station responsive to a current ofcarrier frequency from the ship stationv or from an interfering stationto produce a signal at the land station, a supervisory signal device atsaid switching point, means at the ship station to interrupt the carriersent out from the ship station in accordance. with a code, a selectivearrangement at the 'land station arranged to actuate said supervisorysignal device in response to the carrier frequency from the ship wheninterrupted in accordance with a particular code, but not actuating saidsignal in' response to steady carrier, or carrier interrupted by adifferent code, or in response to interference.

7. In a ship shore radio telephone system, a land radio station havingpaths from a common terminal to a normally disabled radio transmitterand to a radio receiver normally conditioned for operation, meansoperable at will to extend said common terminal to a land circuit, aship station having a normally disabled radio transmitter and a radioreceiver normally conditioned for operation, means at said ship stationto disable the radio receiver thereat and to condition said radiotransmitter at the ship station to send out a carrier wave, means atsaid land station conditioned by the extension of a connection from thecommon terminal of said land. radio station to a land circu't tomaintain the radio transmitter at the land station in disabled conditiononly when the carrier frequency is being received from the ship station,and operable only when so conditioned to disable the radio receiver atthe land station and to condition the radio transmitter thereat foroperation when no carrier is transmitted from the ship station, asupervisory signal device at the common terminal of said land station,means to interrupt the carrier from the ship station in accordance witha code, and means at the land station responsive to the code butunresponsive to interference to actuate said supervisory signal deviceat said common terminal.

8. In a ship shore radio telephone system, a land radio station havingpaths from a common terminal to a normally disabled radio transmitterand to a radio receiver normally conditioned for operation, meansoperable at will to extend said common terminal to a land circuit, aship station having a normally disabled radio transmitter and a radioreceiver normally conditioned for operation, means at said ship stationto disable the radio receiver thereat and to condition said radiotransmitter at the ship station to send out a carrier wave, means atsaid land station conditioned by the extension of a connection Afrom thecommon terminal of said land radio station to a land circuit to maintainthe radio transmitter at the land station in disabled condition onlywhen the carrier Vfrequency is being received from the ship station, andoperable only when so conditioned to disable the radio receiver at theland station and to condition the radio transmitter thereat foroperation when no carrier is transmitted from the ship station, asupervisory signal device at the common terminal of said land station,means at the ship station to interrupt the carrier sent out from theship station in accordance with a code, a selective arrangement at theland station arranged to actuate said supervisory signal in response tothe carrier frequency from the ship when interrupted in accordance witha particular code, but not actuating said signal in response to steadycarrier, or carrier interrupted by a different code, or in response tointerference.

9. In a ship shore radio telephone system, a land radio station having anormally disabled radio transmitter and a plurality of radio receiverseach normally conditioned for operation, a shore controlling andswitching point at which connections may be completed from a landcircuit to said transmitter and from any of said receivers to said landcircuit, a ship station having a normally disabled radio transmitter anda radio receiver normally conditioned for operation, means at said shipstation to disable the radio receiver thereat and to condition saidradio transmitter at the ship station to send out a carrier Wave, meansconditioned by the extension of a connection to a land circuit throughsaid controlling and switching point to maintain the radio transmitterat the land station in disabled condition only when the carrierfrequency is being received by one of said radio receivers at the landstation, and operable only when so conditioned to disable all of saidradio receivers at the land station and condition the radio transmitterthereat for operation when no carrier is transmitted from the shipstation, a supervisory signal device at said switching point, means tointerrupt the carrier from the ship station in accordance with a code,and means responsive to the code but unresponsive to interference toactuate said supervisory signal device at said switching points.

ALBERT FRANKLIN BOWERS.

